Synthesis of Spirocyclic Pyrrolizidineoxyindoles with a Furotropylidene Fragment by 1,3-Dipolar Cycloaddition
摘要:
The 1,3-dipolar cycloaddition of the unstabilized azomethine ylides generated in situ from isatin and proline to the endocyclic C = C bond of the tropylidene ring is absolutely regio- and diastereoselective. The local electrophilicity of the dipolarophile and the local nucleophilicity of the azomethine ylide calculated by the B3LYP/6-31G** method are useful tools for predicting the regioselectivity of cycloaddition. The structure and the three-dimensional structure of the synthesized spiropyrrolizidineoxyindoles were established by correlation NMR spectroscopy and X-ray structural analysis.